SHS Compaction of Titanium Nickelide: Mechanical Activation, Combustion, Structure, and Properties

The study described in this paper pertains to production of consolidated materials using the method of self-propagating high-temperature synthesis with subsequent compaction of hot products (SHS compaction). This method applied to mechanically activated Ni + Ti mixtures helps one obtain pore-free titanium nickelide samples with a diameter of 70 mm and a thickness of 8 mm. Ni + Ti combustion occurs in a reaction mold with neither preliminary heating nor a protective medium. The effect of mechanical activation in a ball mill on the mixture characteristics and combustion parameters is studied. As shown by the analysis of the microstructural characteristics, an increase in the reactivity of mechanically activated Ni + Ti mixtures and the implementation of exothermic interaction during self-propagating high-temperature synthesis are due to a decrease in the crystallite size of Ni particles, an increase in their dislocation density, and the formation of composite Ti–Ni particles. The maximum combustion temperature of the reaction mixture is 1150°C, and the average burning rate is 3.5 cm/s. The main phases of the synthesized alloy are Ti₂Ni, NiTi, and Ni₃Ti. The compressive strength of the samples is 1350 MPa, and the Vickers microhardness is  \(11.1\,\pm\,1.2\)  GPa.